Stretched Rubber Band
2
Whe n the rubber band contr act s, the rubber band gets colder . This means that it is endothermic, which implies the value of delta H, the enthalpy, is positive. Moreover, since it is a s pontaneous reaction, delta G is negative. (It is spontaneous because the polymers are morphing from orderly and in line with each other, to randomness! Then, using Gibbs "#uation, since dG $ dH % Td&, and since the temper ature, T, is always pos it ive , thi s mea ns tha t the d& mus t be positive, and Td& must have a larger magnitude than dH. 'ote )elta & is the entropy value. *+- / TT" 'TI*' This part may sound confusing, so read it a few times &ince when delta G is 0ero, the system is at e#uilibrium, and since after the rubber band reaches a final point of e#uilibrium, the magnitude of Td& must decrease so that the right side of the e#uation reache s 0ero. This mean s that the temperatu re, T, dec rease s ('ow I thin+ that d& increases, since it measures the amount of chaos in the syst em. However , I don1t thin+ that it is incre asing as fast, or fas ter , than the temperature is decreasing.! Ok, cool picture: &tretched rubber band 2ontracted 3ubber band
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Homework question from chemistry!
Transcript of Stretched Rubber Band
When the rubber band contracts, the rubber band gets colder
When the rubber band contracts, the rubber band gets colder. This means that it is endothermic, which implies the value of delta H, the enthalpy, is positive. Moreover, since it is a spontaneous reaction, delta G is negative. (It is spontaneous because the polymers are morphing from orderly and in line with each other, to randomness!!!)
Then, using Gibbs Equation, since dG = dH - TdS, and since the temperature, T, is always positive, this means that the dS must be positive, and TdS must have a larger magnitude than dH. Note: Delta S is the entropy value.OkPAY ATTENTION! This part may sound confusing, so read it a few times
Since when delta G is zero, the system is at equilibrium, and since after the rubber band reaches a final point of equilibrium, the magnitude of TdS must decrease so that the right side of the equation reaches zero. This means that the temperature, T, decreases! (Now I think that dS increases, since it measures the amount of chaos in the system. However, I don't think that it is increasing as fast, or faster, than the temperature is decreasing.)
Ok, cool picture:
Stretched rubber band:
Contracted Rubber band:
